Nanocrystalline magnetite and Mn-Zn ferrite particles via the polyol process: Synthesis and magnetic properties

Nanocrystalline Fe3O4 and Mn-Zn ferrite powders with crystallite sizes of 10 and 7 nm, respectively, and narrow size distribution were synthesized in a triethylene glycol medium. Mn-Zn ferrite particles with crystallite size of 9 and 12 nm were obtained after annealing of the as prepared ferrite particles at 300 and 500 degrees C, respectively. The saturation magnetization at 5 K of the Mn-Zn ferrite obtained at 300 degrees C (79 emu g(-1)) is smaller than that of the bulk material. Hysteresis loop measurements indicate ferrimagnetic behavior at 5 K and superparamagnetic behavior at 295 K. The Mn-Zn ferrite nanocrystals obtained at 500 degrees C, however, exhibit a smaller M-s compared to the ferrite annealed at 300 degrees C indicating a change in the cation distribution. (C) 2011 Elsevier B.V. All rights reserved.